Tube-shell heat exchanger



Jan. 10, 1967 LM-NUNEMAKER v 3,297,081

TUBE-SHELL HEAT EXCHANGER Filed Sept. 2, 1965 ION 12 F IG E JNVENTORF 153761? N Name/mm? BY fi /wves 1' 595720 Joy/v 5. AW A 4:

United States Patent G 3,297,ll81 TUBESHELL HE T EXCHANGER Lester M. Nnnemaker, Buffalo, N.Y., assignor to American Radiator & Standard Sanitary Corporation, New York, N.Y., a corporation of Delaware Filed Sept. 2, 1965, Ser. No. 484,612 2 Claims. (Cl. 165-159) This invention relates to tube-shell heat exchangers wherein fluid of one temperature flows through the tube interiors, and fluid of another temperature flows through the shell around the tubes, whereby the different fluids enjoy heat transfer relation with one another.

One object of the present invention is to provide a tubeshell heat exchanger wherein the shell fluid is baffled by means of low cost wall surfaces formed integrally with the tubes.

Another object is to provide a tube-shell heat exchanger wherein the tubes can be easily and inexpensively assembled into the shell.

A further object is to provide a tube-shell heat exchanger wherein the tubes can be assembled into the shell without inserting them through aligned openings in baffle sheets, thereby facilitating the assembly operation.

An additional object is to provide a tube-shell heat exchanger wherein leakage around the shell fluid baflies is not detrimental to heat exchange efiiciency.

A still further object is to provide a tube-shell heat exchanger wherein intermediate areas of the tubes are enlarged to form baffles and tube support surfaces, thus eliminating the tube spacer sheets which are customarily employed.

A still further object of the invention is to provide a tube-shell heat exchanger which economizes on weight and materials.

Other objects of this invention will appear from the following description and appended claims, reference being had to the accompanying drawings forming a part of this specification wherein like reference characters designate corresponding parts in the several views.

In the drawings:

FIGURE 1 is a longitudinal sectional view taken through a tube-shell heat exchanger embodying the invention;

FIG. 2 is a sectional view taken on line 2-2 in FIG. 1;

FIG. 3 is an enlarged fragmentary sectional view taken on line 33 in FIG. 2;

FIG. 4 is an enlarged sectional view taken on line 44 in FIG. 3;

FIG. 5 is a longitudinal sectional view taken through a second tube-shell heat exchanger embodying the invention;

FIG. 6 is a longitudinal sectional view taken through a third tube-shell heat exchanger having features of the invention embodied therein; and

FIG. 7 is a fragmentary sectional view taken through a modification of the FIG. 1 embodiment.

Before explaining the present invention in detail, it is to be understood that the invention is not limited in its application to the details of construction and arrangement of parts illustrated in the accompanying drawings, since the invention is capable of other embodiments and of being practiced or carried out in various ways. Also, it is to be understood that the phraseology or terminology employed herein is for the purpose of description and not of limitation.

As shown in FIG. 1 of the drawings, the invention ernbodies a tube-shell heat exchanger 10 comprising a bundle of tubes 12 arranged within a tubular shell 23. Each tube 12 is of circular cross section, but is provided with expanded wall enlargements 16 at spaced points therealong which form baflles for directing the shell fluid in tortuous paths as it proceeds from the inlet 13 to the outlet 15. As shown best in FIG. 4, each tube enlargement 16 is of hexagonal cross section, with adjacent enlargements having their flat outer faces 18 substantially engaged with one another to prevent any appreciable flow of shell fluid between the substantially engaged faces. In the illustrated embodiments of the invention the end portions of the tubes are expanded at 20 and 22 to assume hexagonal configurations of the same perimetrical outline as the hexagonal enlargements 16.

As alternates to the hexagonal configuration it is possible to make the enlargements 16 and expanded ends 20, 22 triangular or square in cross section. The enlargements may be formed by the well known hydro-forming process wherein the tubes are positioned between upper and lower elongated dies, and high. pressure fluid is admitted to the tube interiors to bulge the tube walls against hexagonal chamber surfaces formed at spaced points along the dies. The dies may have lengths corresponding to the lengths of the tubes, thereby permitting all of the enlargements in a given tube to be formed during a single hydroforming operation. The expanded ends 20 and 22 may be mechanically die-formed prior to formation of the tube enlargements.

Shell 23 of the heat exchanger may be formed of two half sections 25 and 26, said sections having flanges 28 which abut against one another, suitable seam welds being formed between the respective abutting flanges to fabricate the complete shell. The shell inner surfaces mate with and conform to the outer perimetrical outline of the tube bundle as defined by the expanded end portions 20 and 22 of the outermost tubes in the bundle.

In fabricating the heat exchanger the expanded end portions 20 and 22 of each tube may be coated with solder, after which the various tubes may be positioned in the lower shell half section 26. The ends of the tubes may then be heated to solder the adjacent surfaces of the expanded ends 20 and 22 together, thus sealing the spaces between adjacent tube ends so that in the completed heat exchanger the tube fluid is isolated from the shell fluid.

Before or after the ends of the tubes have been soldered together, the upper shell section 25 may be positioned on the lower shell section, and the flanges 28 welded together to form the complete tube-shell unit. The heat exchanger may be completed by non-illustrated headers having fluid entrance or exit openings communicating with the open ends of tubes 12.

If desired, not only the expanded ends 22 but the intermediate enlargements 16 may also be coated with sol der. After assembly of the two shell halves the entire unit may be placed in a furnace and the whole structure soldered together to form an integrally bonded unit of tube enlargements to tube enlargements and tube enlarge ments to shell configuration as shown in FIG. 2.

Shell 23 may if desired be formed with a cylindrical cross section as shown in FIG. 7. In that event spacers 29 would preferably be provided between the outer flat surfaces of the hexagonal enlargements and the inner surfaces of the shell. Additional spacers would be provided between the outer flat faces of the expanded tube ends and the shell inner surfaces. The cylindrical shell shape of FIG. 7 is somewhat stronger than the corrugated shape of FIG. 2, but suffers somewhat because of the need for spacers 29.

It will be noted that in the FIG. 1 embodiment the individual tubes in the lower half section 26 of the shell have two groups of hexagonal enlargements 37 and 38, and that the individual tubes occupying the upper half section 25 of the shell have two groups of enlargements 39 and 40. The spacing between enlargements 37 and expanded ends 20 is the same as the spacing between enlargements 4t and expanded ends 22. Similarly, the spacing between enlargements 37 and 38 is the same as the spacing between enlargements 39 and 40. The upper tubes may be considered as having their enlargements offset toward ends 22, and the lower tubes may be considered as having their enlargements offset toward ends 24 It will be seen that the tubes in shell section 26 are identical with the tubes in shell section 25, except that they are turned end-for-end when they are positioned to form the tube bundle. All of the tubes may be processed in the same die, which makes for a low tooling cost.

The baffling provided by the various enlargements 37, 38, 39 and 40 causes the shell fluid entering through inlet 13 to take a tortuous, sinuous path as it travels toward outlet 15. Thus the shell fluid has an advantageous heat transfer relation with the fluid flowing through the tube interiors. It is desirable but not essential that each of the tube enlargements have intimate engagement with the flat surfaces 18 of adjacent enlargements. A slight spacing between adjacent surfaces 18 will allow some shell fluid to pass through the baffle, but such fluid is necessarily very close to the tube wall as defined by the wall enlargement, and the fluid thus enjoys a very favorable heat transfer relation to the interior tube fluid.

It will be appreciated that the abutting tube enlargements function not only as baffles but also as reinforcements and support mechanism for the tubes since they tend to maintain the tubes in their true axial positions free from bending or weaving under the influence of the shell fluid pressure or vibrational conditions.

FIG. 1 illustrates an embodiment of the invention wherein the inlet 13 is located in shell section 25, and outlet 15 is located in shell section 26. Both the inlet and outlet may however be located in the same shell section as shown in FIG. 5. FIG. 5 also illustrates a modifled tube arrangement wherein the center row of tubes has a greater number of tube enlargements than the three outer rows adjacent the upper and lower areas of the heat exchanger shell. The overlapping baffle arrangement of FIG. 5 may advantageously be used when the spacing between adjacent bafiies is designed to be relatively small, the objective in any given instance being to maintain, insofar as possible, a fairly constant linear shell fluid velocity between inlet 13 and outlet 15. This is achieved by maintaining the effective cross sectional area of the flow path fairly uniform throughout the different portions of the shell. When the tube enlargements are fairly close together it is necessary to overlap the enlargements in the center row or rows of tubes in an attempt to maintain a fairly constant cross sectional path throughout the shell.

The baffling provided by the tube enlargement arrangements of FIGS. 1 and 5 is advantageous in that it provides predictable heat exchange effects for different size heat exchangers and different pressure, temperature conditions; therefore the FIG. 1 and FIG. 5 arrangements are preferred arrangements because they enable the manufacturer to anticipate different customer requirements without expensive laboratory or field tests. However, some advantageous results may be obtained by the arrangement of FIG. 6 wherein the tube enlargement baffies may not give the same predictable results for a range of different exchangers. As shown in FIG. 6, the tube enlargements are arranged in what might be termed a random fashion. Certain of the enlargements are shown engaged with the enlargements of adjacent tubes, and certain of the other tube enlargements are spaced from the surfaces of adjacent tubes. Each of the tube enlargements provides some baflling of the shell fluid, and thus tends to improve the heat exchange efficiency over that of conventional smooth circular tubes. If desired some conventional tubes (with expanded ends) could be used in the FIG. 6 exchanger.

The invention has been described in various specific embodiments, but it will be appreciated that the invention may be practiced in other forms as come within the scope and spirit of the appended claims.

What is claimed is:

1. A heat exchanger comprising a tubular shell; spaced parallel heat exchange tubes of generally circular cross section extending axially within the shell for conducting fluid of one temperature through the tube interiors; the tubes having expanded end portions providing flat surfaces which abut against one another to seal and space the tubes from each other and from the shell; an inlet for introducing fluid of another temperature into the shell to permit same to flow around the outsides of the tubes; an outlet for discharging the second fluid out of the shell; each of said tubes having at least two integral flat-surfaced enlargements formed at spaced points therealong; said tubes including first and second groups of tubes located on opposite sides of an imaginary longitudinal diametrical plane bisecting the shell; the enlargements in adjacent tubes of a given group being engaged with one another to preclude any appreciable flow of shell fluid through the enlargement-to-enlargement joints; the enlargements in the tubes of the first group being staggered axially from the enlargements in the tubes of the second group, whereby the shell fluid travels in a sinuous path as it flows from the inlet to the outlet; said shell having a constant cross section from end-to-end; said shell having an internal configuration which mates with and conforms to the fiat surfaces of the tube end portions and tube enlargements.

2. The heat exchanger of claim 1 wherein the shell is formed of a multiplicity of shell sections, each section extending the full length of the shell, said sections being secured .together along their longitudinal edges to form the complete shell.

References Cited by the Examiner UNITED STATES PATENTS 1,907,867 5/1933 Potter -161 X 1,995,768 3/1935 Fesenmaier 165--148 X 2,373,157 4/1945 Worth 165-159 X 2,388,721 11/1945 Clancy 165-159 2,396,650 3/1946 Hannah 165-148 2,449,922 9/1948 Andersen 165148 MEYER PERLIN, Primary Examiner.

ROBERT A. OLEARY, Examiner.

A. W. DAVIS, Assistant Examiner. 

1. A HEAT EXCHANGER COMPRISING A TUBULAR SHELL; SPACED PARALLEL HEAT EXCHANGE TUBES OF GENERALLY CIRCULAR CROSS SECTION EXTENDING AXIALLY WITHIN THE SHELL FOR CONDUCTING FLUID OF ONE TEMPERATURE THROUGH THE TUBE INTERIORS; THE TUBES HAVING EXPANDED END PORTIONS PROVIDING FLAT SURFACES WHICH ABUT AGAINST ONE ANOTHER TO SEAL AND SPACE THE TUBES FROM EACH OTHER AND FROM THE SHELL; AN INLET FOR INTRODUCING FLUID OF ANOTHER TEMPERATURE INTO THE SHELL TO PERMIT SAME TO FLOW AROUND THE OUTSIDES OF THE TUBES; AN OUTLET FOR DISCHARGING THE SECOND FLUID OUT OF THE SHELL; EACH OF SAID TUBES HAVING AT LEAST TWO INTEGRAL FLAT-SURFACED ENLARGEMENTS FORMED AT SPACED POINTS THEREALONG; SAID TUBES INCLUDING FIRST AND SECOND GROUPS OF TUBES LOCATED ON OPPOSITE SIDES OF AN IMAGINARY LONGITUDINAL DIAMETRICAL PLANE BISECTING THE SHELL; THE ENLARGEMENTS IN ADJACENT TUBES OF A GIVEN GROUP BEING ENGAGED WITH ONE ANOTHER TO PRECLUDE ANY APPRECIABLE FLOW OF SHELL FLUID THROUGH THE ENLARGEMENT-TO-ENLARGEMENT JOINTS; THE ENLARGEMENTS IN THE TUBES OF THE FIRST GROUP BEING STAGGERED AXIALLY FROM THE ENLARGEMENTS IN THE TUBES OF THE SECOND GROUP, WHEREBY THE SHELL FLUID TRAVELS IN A SINUOUS PATH AS IT FLOWS FROM THE INLET TO THE OUTLET; SAID SHELL HAVING A CONSTANT CROSS SECTION FROM END-TO-END; SAID SHELL HAVING AN INTERNAL CONFIGURATION WHICH MATES WITH AND CONFORMS TO THE FLAT SURFACES OF THE TUBE END PORTIONS AND TUBE ENLARGEMENTS. 